Discussions on accuracy of modified KDP method applied to simultaneous measurements of unsteady flow rates, pressures and impedances for pulsating oil flows in a pipe

When a liquid flow in a pipe is accelerated or decelerated, a differential pressure is kinetically induced between two separate sections of the liquid column. This fact has been utilized to measure an unsteady flow rate, and that way of measurement is called "Kinetic Differential Pressure (KDP) Method". In the present paper, the KDP method is modified so as to find oscillatory flow rates, pressures and hydraulic impedances simultaneously at any section in pulsating pipe flows of oil from the pressure data detected at two fixed sections of the pipe. Through being applied to measurements of impedances of a pipe with a closed end and a Helmholtz resonator, the modified KDP method has proved effective enough for pratical use. In actual measurements, it turned out more recommendable from the viewpoint of accuracy to employ differential pressures obtained by electrical subtraction between outputs of the two pressure transducers than to rely upon pressure data alone.